Previously, outboard marine engines have often utilized various mechanical means for accomplishing easier starting. For example, these engines may engage a "warm-up" lever which manually advances the ignition timing and partially opens the carburetor throttle plate. The function of such arrangement is to increase the idle speed and the air/fuel ratio of the engine when it is started. These conditions allow the engine to start easier and run more smoothly until it has warmed up to its standard operating temperature.
More recently, electronic ignition systems have been provided on outboard marine engines. A multi-variable ignition system for outboard marine engines or the like, which selectively adapts ignition scheduling for a number of conditions is illustrated in U.S. Pat. No. 4,858,585, entitled, "Electronically Assisted Engine Starting Means" by Gregry M. Remmers, which was filed on Dec. 11, 1987, and which is assigned to the assignee of the present invention.
A dual schedule ignition system including the advantages of the system disclosed in the '585 Remmers patent and disclosing, inter alia, a novel and improved opto-electronic time base generator and distributor system is described in U.S. continuation-in-part application, Ser. No. 315,147, entitled "Dual Schedule Ignition System" by Gregry M. Remmers, which was filed on Feb. 24, 1989 and which is assigned to the same assignee as the present invention.
An improved ignition system, having a protection system to prevent reverse engine operation is described in a U.S. application Ser. No. 527,556, entitled "System to Prevent Reverse Engine operation", by Gregry M. Remmers, which was filed on May 23, 1990 and which is assigned to the same assignee as the present invention.
The disclosures of Remmers (U.S. Pat. No. 4,858,585), (Ser. No. 315,147) and (Ser. No. 527,556) are hereby expressly incorporated by reference herein.
The opto-electronic time base generator of Remmers (Ser. No. 315,147) is implemented by having an encoder disk with timing features rotated synchronously with the engine crankshaft past an illumination source which is optically coupled to a photo sensitive element. The timing features are positioned on the disk such that each feature is a predetermined number of degrees of engine rotation in duration. A digital waveform is generated indicating the presence or absence of a particular feature and two pulse trains are derived from each pulse of the waveform, where the first is indicative of the leading edge of the feature and the second is indicative of the trailing edge of the feature.
When the encoder disk is rotated in synchronism with the engine crankshaft, the two trains of pulses form a time base where one pulse train is advanced relative to the second pulse train by the duration of each timing feature. The timing of the pulse trains relative to actual crankshaft position is varied by movement of the illumination source and photo-sensitive element relative to the encoder disk and is scheduled based upon various engine operating parameters.
The first train of pulses provides an advanced ignition timing schedule while the second train of pulses provides a nonadvanced ignition timing schedule. An electrical pulse generator and distributor receives the two pulse trains and selects between the two timing schedules based upon receiving an advance signal or a nonadvance signal. Both schedules are inhibited by an inhibit signal. The selected pulse schedule is distributed to the correct cylinders in the firing sequence of the engine to ignite the engine. A control circuit generates the advance, nonadvance, and inhibit signals based upon time, engine temperature, and starting condition.
The time base generator of Remmers (Ser. No. 527,556) further includes a direction feature which is a predetermined number of degrees of engine rotation in duration. The direction feature is located between the timing features for the last cylinder and the first cylinder, and overlaps the synchronizing feature on the encoder disk.
While the aforementioned opto-electronic time base generators are advantageous in use, there are presently a lack of facile methods and apparatus for maintaining them and testing their operabilities. The timing, synchronizing, or direction features may become blocked by dirt or other foreign materials so that the time base signals are adversely affected. Further, the light emitting diodes, the photo-transistors, and other circuits can develop intermittent faults, or wear out totally. It is relatively difficult without a costly dismantling of the encoder and associated circuitry to determine whether these components are working properly or, if there is a problem, to determine whether it originates in the time base generator or the general ignition circuitry. Therefore, it would be highly advantageous if an effective test apparatus could be devised to determine the operability of the time base generator independently of the ignition circuitry.
Because of the opto-electronic time base generator and the capacitive discharge circuitry, ignition systems of this type are timed somewhat differently than normal ignition systems. However, the standard timing light method which strobes on the firing of a particular cylinder to illuminate a reference mark on the crankshaft is still used. This requires that the engine be started and operating, which for an outboard marine engine usually means dismounting it from its watercraft and remounting it on an engine stand. Thus, it would be highly advantageous to devise a maintenance apparatus which would permit the static (nonoperational) timing of the ignition system of an outboard marine engine without the dismounting of the engine from the watercraft.